This invention relates generally to the field of locomotive control, and more particularly to controlling an operation of a remote locomotive in a distributed power train having a communication system for transmission of communication signals between a lead locomotive and a remote locomotive.
Distributed power train operation supplies motive power from a lead locomotive and one or more remote locomotives spaced apart from the lead locomotive in a train consist. Each lead and remote locomotive includes an air brake control system for controlling braking operations and a communication system for exchanging information between lead and remote locomotives over a communication link. Distributed power train operation may be preferable for long train consists to improve train handling and performance, especially for trains operating over mountainous terrain.
A distributed power train control and communications system generates traction and braking commands responsive to operator-initiated control of a traction (or throttle) controller (throttle handle) or a braking controller (brake handle) in the lead unit. The commands are transmitted to the remote locomotives over a radio frequency communications system (such as the LOCOTROL® distributed power train communications system available from the General Electric Company of Schenectady, N.Y.) including receiving and transmitting components at the lead and the remote units for communicating over a radio frequency link (channel).
For example, when the lead unit operator operates the lead-unit throttle controller to apply tractive effort from the lead unit, the distributed power control and communications system commands each remote unit to supply the same tractive effort. Upon execution of the received command, each remote unit responds to the lead unit with a reply message indicating implementation of the tractive effort command. The distributed power control and communications system can be configured to various operational modes that affect interaction between the lead and remote units and the implementation of lead unit commands at the remote unit.
The lead unit also sends other message types to the remote units, such as status request messages, to which the remote units respond by sending a status reply message back to the lead unit. The status reply message indicates the current operational status of the replying remote unit. Messages from the lead locomotive to the remove units and vise versa are typically sent at predetermined time intervals, for example every twenty seconds. If the communications system is inoperative or the communications link between the lead unit and one or more remote units is disrupted (for example, if line-of-sight directivity is lost due to track topology or an interfering object), lead initiated braking and traction commands are not received by the remote unit(s). In particular, if the lead operator commands an increase in tractive effort because the train is climbing a hill, the remote units will not receive the tractive effort command.
Currently, when a remote unit determines there is a communication loss, the remote unit initiates an algorithm to progressively lower the tractive effort to a presumably safe speed. However, reducing the tractive effort at the remote in such a scenario may increase the load requirements of the lead unit slowing the train as it attempts to climb the hill. In addition, the train speed is reduced, which may effect whether the train is able to meet a trip schedule. In a worst case scenario, the reduction in tractive effort at the remote may generate sufficient in-train forces that can break the train and/or cause a train derailment.